The three neotype species of Capnocytophaga can be identified and classified by the specificity of the surface adhesins which are responsible for their coaggregation to various gram positive oral bacteria. The adhesin activities on the surface of Capnocytophaga ochracea were distinguished by sugar inhibition studies. Coaggregation between C. ochracea and strains of (1) Streptococcus sanguis, (2) Actinomyces viscosus - Antinomyces naeslundii and (3) Actinomyces israelii were inhibited by low concentrations of rhamnose (1mM), high concentrations of rhamnose (10mM) or combinations of rhamnose and sialic acid, respectively. Capnocytophaga sputigena coaggregates with the same strains of the A. viscosus - A. naeslundii cluster and A. israelii group as C. ochracea; these interactions are inhibited by high concentrations of rhamnose (10mM) or rhamnose and sialic acid, respectively. C. gingivalis coaggregates only with strains of A. israelii in a sialic acid sensitive interaction. Naturally occurring coaggregation defective mutants of C. ochracea were isolated which paralleled the phenotypes of C. sputigena and C. gingivalis, that is, the respective coaggregation patterns of these mutants and their sugar inhibition profiles corresponded perfectly with the two neotype species. The reciprocity exhibited by antisera prepared against C. ochracea or C. gingivalis in blocking coaggregation of both gliders with their respective partners indicates that the adhesins on these two organisms are not only functionally homologous, but that they may actually share a degree of structural homology as well. Ribitol-5-P dehydrogenase was purified to homogeneity from ribitol-grown cells of Lactobacillus casei C116 and compared to the xylitol-5-P dehydrogenase from L. casei C183. This key component of the ribitol metabolizing pathway was found to be physically and kinetically distinct from the xylitol-5-P dehydrogenase. No immunological homology could be demonstrated between the two enzymes.